The victim was treated at the scene before being taken to Westmead Hospital where he is reported to be in a serious condition.

A crime scene has been established and police are investigating.

"The shooting is said to have occurred in the back yard of a house in Merrylands," Inspector Bradfield Peters told reporters.

"Essentially, someone has come in and shot in the backyard of the house, this is we have been told. Whether they are the exact circumstances, we are still trying to determine."

In the wake of the shooting, police are said to have a close eye on a wedding that will involve the Ibrahim and Mehajer families on Saturday.

Police are closely monitoring a wedding that will involve the Ibrahim and Mehajer families today. It follows a shooting at of Semi Ngata, the long-time bodyguard of John Ibrahim, at Merrylands. #Merrylands#7Newspic.twitter.com/vRdgNyLYV7